Fix useLeaveDetection to always invoke latest callback

[som-sm]

The useLeaveDetection hook currently sets up the mouseleave event listener only once (due to the empty useEffect dependency). This means the hook always invokes the very first onLeave callback passed to it, rather than the latest one.

haiku/lib/hooks/useLeaveDetection.ts

Lines 3 to 12 in 259ab50

	export function useLeaveDetection(
	onLeave: (this: HTMLElement, ev: MouseEvent) => any,
	) {
	useEffect(() => {
	document.documentElement.addEventListener('mouseleave', onLeave);
	return () =>
	document.documentElement.removeEventListener('mouseleave', onLeave);
	}, []);
	}

Now, this works in the documentation example because it uses the callback approach to update the state.

haiku/docs/src/components/Demo/LeaveDetection.js

Lines 5 to 6 in 259ab50

	const [leaveCount, setLeaveCount] = React.useState(0);
	useLeaveDetection(() => setLeaveCount((s) => s + 1));

However, if the state is updated directly by passing a value, then the hook breaks, because it fails to invoke the latest callback everytime the mouseleave event occurs, instead it keeps calling the initial callback (() => setLeaveCount(0 + 1)).

const [leaveCount, setLeaveCount] = React.useState(0); 
useLeaveDetection(() => setLeaveCount(leaveCount + 1));

A simple fix would be to add onLeave to the useEffect dependency array:

export function useLeaveDetection( 
   onLeave: (this: HTMLElement, ev: MouseEvent) => any, 
 ) { 
   useEffect(() => { 
     document.documentElement.addEventListener('mouseleave', onLeave); 
  
     return () => 
       document.documentElement.removeEventListener('mouseleave', onLeave); 
-   }, []);
+   }, [onLeave]);
 }

While this works, it's not ideal. Each time a new callback is passed, a new event listener is set up. Since it's easy to pass a new callback on every render, this places the burden of memoizing the callback on the user, which doesn’t make for a great API.

This PR updates the implementation to fix the stale callback issue while ensuring the listener is set up only once. I've also added a comprehensive set of tests to verify that everything works as expected.